1. Field of the Invention
The invention relates to a process for producing composites comprising inorganic material, organic polymer and silane adhesion promoter.
2. Description of the Related Art
Organosilicon compounds having unsaturated organic functional groups such as vinyl, acryloyl or methacryloyl groups, are widely used as adhesion promoters between inorganic and organic materials, for example in sizers for glass fibers, as crosslinking agents in organic polymers or for the treatment of fillers.
An important use of such silanes is moreover the improvement, achievable by the adhesion-promoting effect, of the mechanical properties of artificial stones which can be produced from inorganic fillers and curable, organic resins.
The silanes carrying unsaturated groups can be added both according to EP 483280 B1 for the pretreatment of corresponding fillers and for the “in situ” treatment directly in the formulation of the end product, as described in JP 3209084 B.
In the production of artificial stone products based on organic resins and inorganic fillers, a distinction is made essentially between two products, namely so-called solid surface products, which generally consist of ATH (aluminum trihydrate)-filled polymethyl methacrylate (PMMA), and the so-called quartz surface products, which are generally based on SiO2-filled unsaturated polyester resins (UP resins). Of particular importance are processes in which the silane is used in situ and in which the mixture consisting of the inorganic, generally silicate fillers, the UP resin and optionally additional additives is compacted prior to curing in vacuo and with vibration, as is carried out in the so-called Breton process described in U.S. Pat. No. 4,698,010.
A disadvantage of the silane adhesion promoters typically used to date is the relatively high price which, in spite of the small amount used (in general about 0.05-1.0% by weight, based on the total raw material mixture), accounts for a not inconsiderable part of the total raw material costs. Moreover, a reduction in the tendency to soiling and an improvement in the hot water resistance and weathering resistance of the artificial stone products produced according to the present state of the art would be desirable.
JP 2004099351 describes the use of a silane adhesion promoter together with a further alkoxy silane or the (co)hydrolyzates thereof for the surface pretreatment of fillers for use in artificial marble.
JP 3072697 B describes the use of methyl or ethyl silicate and polymers thereof in the mixture with a silane adhesion promoter having unsaturated groups. Once again, the use of such a mixture for the pretreatment of inorganic fillers, in this case ATH, is described.
JP 3209084 B describes the use of mixtures consisting of a thermally curable organic resin and inorganic powders or fibers, which are treated with a mixture of alkoxysilanes having unsaturated groups and siloxanes, in order to increase the water resistance. The addition of these components can be effected both to the filler and to the mixture of the filler with the resin.